Currently, ethylene oxide (EO) is the agent of choice for virtually all of the gaseous sterilization of consumer products performed in the United States. EO, however, has a number of properties which limit its use as a sterilant. For example, EO is highly flammable and highly explosive. For this reason, all EO sterilization facilities must include damage-limiting construction and all equipment used in the EO sterilization process must be explosion proof In addition, high concentrations of EO are acutely toxic for humans, and EO has been implicated as a carcinogen in laboratory animals. EO sterilization plants must, therefore, be outfitted with expensive equipment to minimize exposure of facility personnel to EO and to prevent escape of EO to the atmosphere outside the facility.
Another disadvantage of EO is that it reacts with chlorine to form ethylene chlorhydrin (ECH) and with water to form ethylene glycol (EG). Both of these byproducts are toxic and must be reduced to safe levels before sterilized materials are released for use. In fact, formation of ECH and EG preclude the use of EO for sterilization of a number of food products for which it would otherwise be a very useful sterilant.
Over the last fifty years, a number of other gases that lack one or more of the disadvantages of EO have been tested as sterilants. These gases include, for example, hydrogen peroxide, ozone and chlorine dioxide. However, no other gas has proven to be as efficacious as EO for use in large volume industrial sterilizers. The most common reason for failure of these gases as useful sterilants has been inadequate permeation of the gases through packaging materials and into lumens and interstices of the product being sterilized. Failure to permeate may be due to a number of factors including size of the sterilant molecule, reactivity of the sterilant molecule with outer packaging materials prior to reaching the target material, and degradation of the sterilant molecule prior to reaching the target material.
A number of commercial fumigants are presently used to treat foodstuffs and other stored commodities. The most widely used fumigants are methyl bromide, hydrogen phosphide, carbon dioxide, and hydrogen cyanide. Many of these compounds pose hazardous conditions for application personnel and can form deleterious residues in the foodstuffs and commodities that are treated. Methyl bromide, the most widely used fumigant, has been identified as an ozone layer depleting agent and is slated, under the Montreal Protocols of 1997, to be banned by the year 2005. One important factor that differentiates the above listed fumigants from other sterilants is their ability to readily permeate granular or powdered products, which allows the fumgant to contact the infesting pests in such products.
Some of the above-mentioned traditional sterilants or fumigants have been identified with the formation of carcinogens and mutagens which thus limit the products that can be treated.
Other procedures that have been developed to treat products utilize heat, ionizing radiation, and other chemical compounds. All of these procedures are potentially detrimental to the products' nutritional, physical and/or chemical attributes and thus make them undesirable.
Thus, a means to reduce biological loads in consumer products to eliminate human pathogens while maintaining product stability remains a necessity. Accordingly, there remains a need for better alternative methods and apparatus for reducing the biological load on consumer products.